In advance of Halloween, Burger King unveiled a new whopper with black buns and A1 steak sauce in late September. The company called it the Halloween Whopper.

Fans of the Whopper were excited to try the new menu item, but after only a few hours, they were left with more than memories and an Instagram picture — some claim their feces had turned greenish blue, as first spotted by First We Feast.

Right away, people started posting the news on Twitter:

Some people are saying the new shade could last multiple days.

One Twitter was less than amused and pointed out that the black bun contains nearly twice as many chemicals and ingredients as the normal sesame seed bun. These ingredients include FD&C Blue #1 and FD&C Yellow #6, which combined, would give you that blue-green color everyone is seeing.